Method of securing deformable sheet metal elements



Oct. 8, 1968 T. A! ROSBOTTOM METHOD OF SECURING DEFORMABLE SHEET METAL ELEMENTS Filed Ju 1y 25, 1967 4 Sheets-Sheet Inventor TOM Get. 8, 1968 T. A. ROSBOTTOM 3,404,648

METHOD OF SECURING DEFORMABLE SHEET METAL ELEMENTS Invenlor 70I14$ 4 ?0.sBoTToM y v I Oct. 8, 1968 'r. A. ROSBOTTOM 3,404,643

METHQD 0F SECURING DEFORMABLE SHEET METAL ELEMENTS Filed July 25, 1967 4 Sheets-Sheet s Inventor Flo/1A sA. #0330110! METHOD OF SECURING DEFORMABLE SHEET METAL ELEMENTS Filed July 25, 1967 Oct. 8, 1968 T. A. RgBQTTOM 4 Sheets-Sheet 4 Inventor I T/iomsA. PowOrra/ United States Patent m 3,404,648 METHOD OF SECURING DEFORMABLE SHEET METAL ELEMENTS Thomas Albert Rosbottom, Hayes, England, assignor to The Metal Box Company Limited, London, England, a British company Original application May 10, 1965, Ser. No. 454,293. Divided and this application July 25, 1967, Ser. No. 6 9,328 Claims priority, application Great Britain, May 20, 1964, 20,876/64 2 Claims. (Cl. 113-121) ABSTRACT OF THE DISCLOSURE A method of securing ductile materials to one another wherein one of the sheets is superimposed on the other and the two sheets are clamped together, and a portion thereof is deformed substantially into a frustrum of a cone while the sloping sides of the frustrum across a space between rigid walls are impacted at the closed end of the frustrum to extrude metal therefrom into the sloping sides to thereby deform and interlock the sides. One of the sheets mays comprise a pull tab.

Cross reference to related application This application is a division of application Ser. No. 454,293, filed May 10, 1965, now Patent No. 3,359,935.

Background of invention It is usual when securing a pull tab to a container member, such as a can end, provided with a scored removable zone to provide one of the parts with an aperture which fits over a hollow rivet formed in the other part. When the apertured part has been fitted over the rivet the latter is deformed to secure the apertured part in position. These proposals are subject to a number of disadvantages, for instance the punching of the aperture leaves a burr which must be removed and this is a difficult, precise operation under mass production conditions. Should the burr not be fully removed it bears against the root of the rivet, which is the weakest point thereof, when the parts are assembled and this may lead to rupturing of the material during deformation of the rivet. Further, when the metal is drawn to form the rivet the metal is thinned and stretched causing undesirable weakening in the areas where the thinning is most pronounced. It is also necessary that the forming of the rivet and of the aperture be performed separately and the parts assembled after such forming operations.

Summary of invention According to the invention there is provided a method of securing one portion of ductile sheet metal to another by superimposing one on the other and clamping them around the area thereof to be secured, creating from the clamped area a substantially frusto-conical formation the sloping sides of which extend across a space formed between rigid walls, and by impact extrusion causing metal from the closed end of the frusto-conical formation to flow into said slopping sides thereby to effect deformation and interlocking thereof in said space.

One of the sheet metal portions may be the scored removable zone portion of a container member and the other of the sheet metal portions be a part of a pull tab.

Also according to the invention there is provided a container member made of deformable sheet metal and including a scored removable portion, and a deformable sheet metal pull tab secured to the scored removable portion by the method set forth above.

3,404,648 Patented Oct. 8, 1968 Brief description of drawings In order that the invention may be clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which:

FIGURE 1 is a top plan of a can end constructed in accordance with the invention,

FIGURE 2 is an underneath plan of FIGURE 1,

FIGURE 3 is a section, to an enlarged scale, on line III-III, FIGURE 1,

FIGURE 4 is a line drawing made from a microphotograph of two portions of sheet metal secured together by the method and apparatus according to the invention,

FIGURE 5 is a section illustrating apparatus according to the invention,

FIGURES 6 to 9 illustrate diagrammatically the meth od of and apparatus for securing a pull tab to the can end shown in FIGURES 1 to 3,

FIGURE 10 illustrates a modification to the apparatus of FIGURES 6 to 9, and

FIGURE 11 illustrates a modification to a punch sleeve embodied in apparatus according to the invention.

Detailed description of invention Referring to FIGURES l to 4 of the drawings, a container member, shown as a can end ll of known kind, is made of ductile metal and is provided with a scored removable zone 2 defined, in the usual manner, by a score line 3. It is to be understood that the shape of the scored removable zone may, if desired, be other than that shown in FIGURE 1. A pull tab 4, also made of ductile sheet metal, is secured to the scored removable zone by a method which, in accordance with the invention, does not require that either the said zone or the pull tab be provided with an aperture to facilitate the securing of the one part to the other. The pull tab, which may be of a shape other than that shown in the drawings, is interlocked with and secured to the scored removable zone by deformation 5 of the sides of a hollow portion 6 closed at one end 7 and formed by overlying portions 8, 9, FIG- URE 3, of the pull tab and the scored removable zone. The deformation of the sides of the hollow portion is efiected by impact extrusion of the end 7 into the sides of the hollow portion with the result, as can be seen from FIGURES 3 and 4, that the thickness of the top overlying portions 8, 9 is reduced from the starting thickness thereof.

The method of securing the pull tab 4 to the scored removable zone 2 is illustrated in FIGURES 6 to 9. A flat part of the scored removable zone 2 is laid on the face of a base member 10 supported for restricted movement against the action of a spring or springs S indicated diagrammatically in FIGURES 6 and 7, and a flat part of the pull tab 4 is superimposed thereon. Above the base member 10 a parallelsided punch sleeve 11 is supported by a press ram R for reciprocation towards and away from the base member 10 and when the scored removable zone 2 and pull tab 4 are in position on the base member, FIGURE 6, the punch sleeve 11 is moved downward to clamp the scored removable zone and pull tab against the base member, FIGURE 7.

A stationary anvil 12 co-axial with a punch 13 housed in the punch sleeve 11 is associated with the base member 10 and has a head 14 which is of lesser diameter than that of the punch 13 and is tapered, FIGURES 6 to 9, in a manner such as to preserve the largest possible top area together with the sharpest possible incline. In the starting position of the apparatus the head 14 does not project beyond the face of the base member but when the punch sleeve 11 and punch 13 engage the upper face of the two superimposed pieces of metal, FIGURE 7,

3 the resilient loading, shown as springs S1, FIGURE 5, of the punch sleeve 11 reacts against the spring-loading S of the base member 10. The springs S1 for the punch sleeve 11 are stronger than the springs S and the base member is forced to retract, FIGURES 8 and 9. The metal portions clamped around between the base member 10 and the punch sleeve 11 are thus deformed about the frusto-conical head 14 of the anvil and the sloping sides of the hollow frusto-conical formation of the metal portions extend across the space formed by the rigid walls of the sleeve 11 and head 14, FIGURE 8. In FIGURE 5, the can end 1 and the pull tab 4 are, for clarity, shown slightly spaced apart. The impact of the punch 13 against the closed end 7 of the hollow frusto-conical formation causes metal from the closed end 7 to flow into the sloping sides of hollow conical formation thus deforming and interlocking said sides as shown in FIGURES 4 and 9. As the pressure is released suitable means, for example an air cylinder AC, FIGURE 5, causes the punch 13 to be restored to the position thereof shown in FIGURE 6, thereby ejecting the interlocked metal portions from the sleeve 11. The restoring of the base member 10 to the normal position thereof, FIGURE 6, causes the interlocked metal portions to be lifted from the anvil 12.

The punch 13 is slidably housed in the sleeve 11 and the sleeve is loaded as by the springs S1 or a rubber buffer, not shown, so that pressure exerted by the sleeve 11 is not so great as that exerted by the punch 13. The springs S ensure that when the sleeve 11 and punch 13 are raised the interlocked portions are ejected from the head 14.

It will be understood that by using the method just described the two sheets of metal are interlocked and secured one to the other by a single operation and this i not only simplifies the manufacturing process, as compared with the processes previously employed, but also permits the operation to be performed with the least possible disturbance to the metal, thus, also as compared with the processes previously employed, reducing workhardening and the tendency for the metal to fracture or become brittle. The strain on the metal is further reduced by the use of the tapering anvil 12 because by the use thereof the sides of the frusto-cone formed in the metal are not required to be substantially perpendicular. Also, because there are two layers of metal over the areas 15, 16, FIGURE 8, of the frusto-cone, where previously a rivet was weakest, there is with a coupling formed in accordance with the invention a higher factor of safety than has been possible hitherto and this can be of considerable importance in the case of, for example, beer cans which may have a high internal pressure.

The metals from which the can end and pull tab are made may be of any suitable kind deformable by an impact extrusion process and may be alloys of nonferrous metals capable of extrusion under reasonably low pressures. Such metals include aluminium and aluminium alloys.

In the foregoing description there has been described the manner in which a pull tab is secured to a scored removable zone. It is, however, to be understood that the invention may be applied to the securing together of other components. For example, the method may be used for fixing handles to aluminium mugs, cups, saucepans, or drawers; for joining sheet metal in the manufacture of metal cabinets or other rectangular constructions; or in other instances in which it is required to form a metal attachment between two sheets of ductile metal where formerly riveting, or welding, or soldering was employed.

In carrying the invention into effect the preferred range of metal thickness is between 0.010 and 0.025 inch although the thickness will depend on the purpose and nature of the finished article. The tab, or handle, may be of the same thickness as that of the sheet to which it is to be secured or it may be of greater or lesser thickness; again this depends on the purpose. The preferred diameter of a finished coupling is between and inch but this also depends on the purpose and on the thickness of the metal. Further, the coupling may be circular, elongated, square, or of any other suitable shape. The tooling pressures are not critical but one will naturally apply the minimum required to extrude the metal used and this will vary according to the alloy and also according to the area involved.

As illustrated in the drawings, the opposed faces of the anvil 12 and punch 13 are fiat but, if desired these faces may be mating convex/concave surfaces.

If desired, as shown in FIGURE 10, the head 14 of the anvil 12 may be of circular cross-section of leaser diameter than that of the body of the anvil.

In a further modification of the apparatus, the anvil may be as shown in FIGURE 9 or 10 and the punch sleeve portion which with the anvil forms the space in which interlocking is effected is split lengthwise, as at 18, FIGURE 11, to permit lateral extension of the sleeve as the metal is forced into the sleeve about the head of the anvil, and the sleeve is provided with an annular recess 17 which together with the anvil forms the space in which interlocking takes place.

I claim:

1. A method of securing sheets of ductile metal to one another comprising the steps of superimposing one of said sheets on the other, clamping said sheets together around the area thereof to be secured, deforming a portion of said clamped area substantially into a frustrum of a cone extending outwardly of the sheets, and retaining the sloping sides of said frustrum across a space between rigid tool walls while impacting the closed end of said frustrum to extrude metal laterally outwardly therefrom into said sloping sides to thereby deform and interlock said sides outwardly of the sheets within said space.

2. A method of securing a ductile metal container member to a ductile metal pull tab comprising the steps of scoring a portion of said container member to render said portion removable, superimposing said pull tab on said scored portion of the container member, clamping together said tab and scored portion of the container member around an area to be secured, deforming a portion of said clamped area substantially into a frustrum of a cone extending outwardly of the container member and pull tab, and retaining the sloping sides of said frustrum across a space between rigid tool walls while impacting the closed end of said frustrum to extrude metal laterally outwardly therefrom into said sloping sides and thereby deform and interlock said sides outwardly of the container member and pull tab in said space.

References Cited UNITED STATES PATENTS 2,992,857 7/1961 Lemmerz. 3,151,766 10/1964 Henchert. 3,198,155 8/1965 Fraze 29509 X CHARLIE T. MOON, Primary Examiner. 

